1. Field of the Invention
The present invention relates generally to the field of multi input multi output (MIMO) receivers and particularly to a method and apparatus for optimizing complementary code keying (CCK) receiver design using independent equalizer combining in the time domain.
2. Description of the Prior Art
As computers have gained enormous popularity in recent decades, so have networking the same allowing for access of files by one computer from another. More recently and with the advent of wireless communication, remote and wireless networking of computers is gaining more and more notoriety among personal users, small and large business owners, factory facilities and the like.
With regard to the wireless networking of personal computers including laptops, a particular modem, namely modems adapted to the IEEE 802.11a or 802.11g industry standard, are commonly employed. That is, an antenna is placed inside or nearby the personal computer and an RF chip receives signal or data through the antenna and an analog-to-digital converter, typically located within the personal computer (PC), converts the received signal to baseband range. Thereafter, a baseband processor is employed to process and decode the received signal to the point of extracting raw data, which may be files transferred remotely and wireless, from another PC or similar equipment with the use of a transmitter within the transmitting PC.
To improve reception of data at higher rates wireless receivers often employ multiple antennae. In the design of multi input multi output (MIMO) transceivers new technical challenges such as the requirement to combine multiple channels emerge. Conventional 802.11g compliant receivers decode data modulated in both the time (complementary code keying (CCK)) and frequency domains (orthogonal frequency division multiplexing (OFDM)).
Conventional approaches to multi antennae receiver designs include maximum antenna approach wherein the antenna with maximum received signal power is chosen for reception. Other conventional approaches include an all time domain design which is a stand-alone module but does not allow the advantage of frequency domain combining that is more suitable for OFDM processing. The all time domain design also has the disadvantage of having a costly implementation in terms of silicon die area. Moreover, a design restricted to frequency domain, which benefits OFDM reception, does not necessarily improve the CCK receiving portion of the receiver.
Combining of signals before equalization in the conventional 802.11g compliant receivers is sub-optimal due to potential destructive effects of addition of channels off the main tap. In addition, holding the computed maximum ratio combining (MRC) parameters constant during the subsequent equalization process may not yield the highest quality signal for CCK decoding.
Thus, it is desirable to develop a method and apparatus for improving the performance of the MIMO receivers by optimizing the equalization process. In addition, the effects of multi-path channels should be minimized by improving the MRC parameters used in the equalization process.